Implement Switch expression evaluation

src/core/Elsa.Core/Activities/ControlFlow/Switch/Switch.cs

@@ -18,7 +18,7 @@ namespace Elsa.Activities.ControlFlow
         DisplayName = "Switch",
         Category = "Control Flow",
         Description = "Evaluate multiple conditions and continue execution depending on the results.",
-        Outcomes = new[] { OutcomeNames.Done }
+        Outcomes = new[] { OutcomeNames.Default }
     )]
     public class Switch : Activity, INotificationHandler<ScopeEvicted>
     {
@@ -55,8 +55,9 @@ namespace Elsa.Activities.ControlFlow
             }
 
             var matches = Cases.Where(x => x.Condition).Select(x => x.Name).ToList();
-            var results = Mode == SwitchMode.MatchFirst ? matches.Any() ? new[] { matches.First() } : new string[0] : matches.ToArray();
-            var outcomes = results;
+            var hasAnyMatches = matches.Any();
+            var results = Mode == SwitchMode.MatchFirst ? hasAnyMatches ? new[] { matches.First() } : new string[0] : matches.ToArray();
+            var outcomes = hasAnyMatches ? results : new[] { OutcomeNames.Default };
 
             return Outcomes(outcomes);
         }

src/core/Elsa.Core/Activities/ControlFlow/Switch/SwitchHandler.cs

@@ -0,0 +1,59 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Runtime.CompilerServices;
+using System.Threading;
+using System.Threading.Tasks;
+using Elsa.Expressions;
+using Elsa.Serialization;
+using Elsa.Services.Models;
+
+namespace Elsa.Activities.ControlFlow
+{
+    public class SwitchHandler : IExpressionHandler
+    {
+        private readonly IContentSerializer _contentSerializer;
+        public string Syntax => "Switch";
+
+        public SwitchHandler(IContentSerializer contentSerializer)
+        {
+            _contentSerializer = contentSerializer;
+        }
+
+        public async Task<object?> EvaluateAsync(string expression, Type returnType, ActivityExecutionContext context, CancellationToken cancellationToken)
+        {
+            var caseModels = TryDeserializeExpression(expression);
+            var evaluatedCases = await EvaluateCasesAsync(caseModels, context, cancellationToken).ToListAsync(cancellationToken);
+            return evaluatedCases;
+        }
+
+        private async IAsyncEnumerable<SwitchCase> EvaluateCasesAsync(IEnumerable<SwitchCaseModel> caseModels, ActivityExecutionContext context, [EnumeratorCancellation] CancellationToken cancellationToken)
+        {
+            var validCaseModels = caseModels.Where(x => x.Expressions != null && !string.IsNullOrWhiteSpace(x.Syntax) && x.Expressions.ContainsKey(x.Syntax)).ToList();
+            var evaluator = context.GetService<IExpressionEvaluator>();
+
+            foreach (var caseModel in validCaseModels)
+            {
+                var syntax = caseModel.Syntax!;
+                var expression = caseModel.Expressions![syntax];
+                var result = await evaluator.EvaluateAsync<bool>(expression, syntax, context, cancellationToken);
+
+                yield return new SwitchCase(caseModel.Name, result);
+            }
+        }
+
+        private IList<SwitchCaseModel> TryDeserializeExpression(string expression)
+        {
+            try
+            {
+                return _contentSerializer.Deserialize<IList<SwitchCaseModel>>(expression);
+            }
+            catch
+            {
+                return new List<SwitchCaseModel>();
+            }
+        }
+
+        public record SwitchCaseModel(string Name, IDictionary<string, string>? Expressions, string? Syntax);
+    }
+}

src/core/Elsa.Core/Extensions/ElsaServiceCollectionExtensions.cs

@@ -1,5 +1,6 @@
 using System;
 using Elsa;
+using Elsa.Activities.ControlFlow;
 using Elsa.Activities.Signaling;
 using Elsa.Activities.Signaling.Services;
 using Elsa.Activities.Workflows;
@@ -147,6 +148,7 @@ namespace Microsoft.Extensions.DependencyInjection
                 .TryAddProvider<IExpressionHandler, LiteralHandler>(ServiceLifetime.Singleton)
                 .TryAddProvider<IExpressionHandler, VariableHandler>(ServiceLifetime.Singleton)
                 .TryAddProvider<IExpressionHandler, JsonHandler>(ServiceLifetime.Singleton)
+                .TryAddProvider<IExpressionHandler, SwitchHandler>(ServiceLifetime.Singleton)
                 .AddScoped<IExpressionEvaluator, ExpressionEvaluator>();
 
             // Workflow providers.

src/designer/elsa-workflows-studio/src/plugins/switch-plugin.tsx

@@ -0,0 +1,26 @@
+import {ElsaPlugin} from "../services/elsa-plugin";
+import {eventBus} from '../services/event-bus';
+import {ActivityDesignDisplayContext, EventTypes, SyntaxNames} from "../models";
+import {h} from "@stencil/core";
+import {parseJson} from "../utils/utils";
+import {SwitchCase} from "../components/editors/properties/elsa-switch-cases-property/models";
+
+export class SwitchPlugin implements ElsaPlugin {
+  constructor() {
+    eventBus.on(EventTypes.ActivityDesignDisplaying, this.onActivityDesignDisplaying);
+  }
+
+  onActivityDesignDisplaying(context: ActivityDesignDisplayContext) {
+    const activityModel = context.activityModel;
+    
+    if (activityModel.type !== 'Switch')
+      return;
+
+    const props = activityModel.properties || [];
+    const syntax = 'Switch';
+    const casesProp = props.find(x => x.name == 'Cases') || { expressions: {'Switch': ''}, syntax: syntax };
+    const expression = casesProp.expressions[syntax];
+    const cases: Array<SwitchCase> = parseJson(expression) || [];
+    context.outcomes = [...cases.map(x => x.name), 'Default'];
+  }
+}

src/designer/elsa-workflows-studio/src/services/plugin-manager.ts

@@ -8,6 +8,7 @@ import {DefaultDriversPlugin} from "../plugins/default-drivers-plugin";
 import {ForkPlugin} from "../plugins/fork-plugin";
 import {RunJavascriptPlugin} from "../plugins/run-javascript-plugin";
 import {ActivityIconProviderPlugin} from "../plugins/activity-icon-provider-plugin";
+import {SwitchPlugin} from "../plugins/switch-plugin";
 
 export class PluginManager {
 
@@ -19,6 +20,7 @@ export class PluginManager {
       new ActivityIconProviderPlugin(),
       new IfPlugin(),
       new ForkPlugin(),
+      new SwitchPlugin(),
       new HttpEndpointPlugin(),
       new TimerPlugin(),
       new WriteLinePlugin(),

src/scripting/Elsa.Scripting.JavaScript/Extensions/JavaScriptServiceCollectionExtensions.cs

@@ -19,7 +19,7 @@ namespace Microsoft.Extensions.DependencyInjection
                 .AddScoped<ITypeDefinitionProvider, EnumTypeDefinitionProvider>()
                 .AddScoped<ITypeDefinitionProvider, EnumerableTypeDefinitionProvider>()
                 .AddScoped<IJavaScriptService, JintJavaScriptEvaluator>()
-                .AddTransient<IConvertsJintEvaluationResult>(s => new JintEvaluationResultConverterFactory(s).GetConverter())
+                .AddTransient(s => new JintEvaluationResultConverterFactory(s).GetConverter())
                 .AddTransient<IConvertsEnumerableToObject>(s => new EnumerableResultConverter(default))
                 .TryAddProvider<IExpressionHandler, JavaScriptExpressionHandler>(ServiceLifetime.Scoped)
                 .AddNotificationHandlers(typeof(JavaScriptServiceCollectionExtensions));